Postfix stable release 2.8.7

Postfix stable release 2.8.7 is available. This contains a
workaround for a problem that is fixed in Postfix 2.9.

The postscreen daemon, which is not enabled by default,
sent non-compliant SMTP responses (220- followed by 421) when it
could not give a connection to a real smtpd process. These responses
caused some remote SMTP clients to return mail as undeliverable.

The workaround is to hang up after sending 220- without sending
the 421 "sorry" reply; this is harmless.

The complete fix involves too much change for a stable release:
send the 220 greeting, wait for the EHLO command, then send the 421
"sorry" reply and hang up.